1. Field of the Invention
The present invention relates to a portable phone with a detecting unit of contact of an antenna with a human body.
2. Description of the Related Art
A driving source to operate a portable phone circuit is a battery. There is a limit in the charge capacity of the battery, and the power consumption of the portable phone should be suppressed as less as possible. Also, the power consumption at the time of transmission and reception should be suppressed at a minimum.
It is described in Japanese Laid Open Patent Application (JP-A-Heisei 9-162618) that the impedance of an antenna changes when a human body contacts an antenna electrically connected with a transmitting and receiving circuit.
In case of transmission, when the impedance of the antenna changes, all the power of an amplified transmission signal from the transmitting circuit is not irradiated from the antenna and a part of the amplified transmission signal power is reflected as a reflection power. Such reflection is equivalent to the decrease of the gain of the antenna, and therefore it is impossible to transmit the transmission signal with the enough power to a base station so that the transmission performance is degraded. In case of reception, when the antenna contacts the human body, reception performance is also degraded, because the enough reception power can not be received by the receiving circuit due to the impedance change of the antenna.
The technique in which a special circuit is provided to prevent such degradation of the transmission and reception performance is not limited to the above reference. It is known even in Japanese Laid Open Patent Application (JP-A-Heisei 7-23450), and Japanese Laid Open Patent Application (JP-A-Heisei 7-106999).
Another conventional method is known to prevent the degradation of the transmission and reception performance of an antenna of a portable phone. As shown in FIGS. 1 and 4, such a well known portable phone 100 is composed of one antenna 101 and another antenna 102. The antenna 101 is used for the transmission and reception and the antenna 102 is a receive-only antenna. To switch the antennas 101 and 102 and to use one of the two antennas 101 and 102, it is provided with two high frequency switches 103 and 104. By using such two antennas, antenna switching system diversity reception is made possible. The switching of both antennas is carried out by a CPU 105.
As shown in FIGS. 2A and 2B, in TDMA (Time Division Multiple Access) system, the operating time of the portable phone is composed of a transmission time region S1, a reception time region S2 and an idle time S3. As shown in FIG. 3, steps S101, S102 and S103 are repeated in order. During the idle time S3, an electric field intensity output voltage signal 107 is outputted from a receiving circuit 106 shown in FIG. 4 to the CPU 105. As shown in FIG. 5, an electric field intensity output voltage Va corresponding to the electric field intensity of the antenna and an electric field intensity output voltage Vb corresponding to the electric field intensity of the antenna 102 are compared with each other at a step S104 shown in FIG. 6. The antenna having the larger electric field intensity is selected by the CPU 105.
When the human body contacts such one of two antennas, the antenna switching to prevent the degradation of the transmission and reception performance is lost the original meaning.
Therefore, it is desirable to provide to a portable phone having a function to inform a user of the portable phone that the antenna contacts the body of the user. Also, it is desirable to attain the antenna switching function effectively.
Therefore, an object of the present invention is to provide a portable phone with a detecting unit, for notifying contact of an antenna with a human body or decrease of an electric field intensity around the antenna.
Another object of the present invention is to provide a portable phone with a detecting unit, in which contact of an antenna with a human body or decrease of an electric field intensity around the antenna can be notified, and a circuit to be added for the notification is simple so that the rise of a manufacturing cost can be suppressed.
Still another object of the present invention is to provide a portable phone with a detecting unit, in which contact of an antenna with a human body or decrease of an electric field intensity around the antenna can be notified to utilize an antenna switching function effectively.
In order to achieve an aspect of the present invention, a portable phone includes an antenna, a detecting circuit and a notifying section. The detecting circuit detects at least one of contact of the antenna with a user of the portable phone and decrease of an electric field intensity around the antenna, and generates a notice signal based on the detecting result. The notifying section notifies the user of the contact of the antenna with the user in response to the notice signal.
Here, the detecting circuit may detect the contact of the antenna with the user based on power of a reflected signal from the antenna when a transmission signal is supplied to the antenna.
Also, the detecting circuit may detect a voltage of a reflected signal from the antenna when a transmission signal is supplied to the antenna, and detects the contact of the antenna with the user when the detected voltage is equal to or larger than a predetermined value. In this case, the predetermined value can be previously settable by the user.
Also, the detecting circuit may detect impedance change of the antenna and detects the contact of the antenna with the user based on the detected impedance.
Also, the detecting circuit may detect the contact of the antenna with the user during transmission of a transmission signal via the antenna. In this case, the portable phone may further includes a transmitting circuit, a receiving circuit, a high frequency switch selectively connecting the antenna to one of the receiving circuit and the transmitting circuit, and a circulator connecting the high frequency switch with one of the detecting circuit and the transmitting circuit. Also, the circulator includes a 3-input and 1-output circuit, wherein the detecting circuit is connected with the high frequency switch but is not connected with the transmitting circuit, and the transmitting circuit is connected with the high frequency switch but is not connect with the detecting circuit, and the high frequency switch is connected with the detecting circuit but is not connected with the transmission circuit.
Also, the notifying section preferably includes at least one of a vibrator, a speaker and an LED.
Also, it is preferable that the detecting circuit stops the generation of the notice signal when the antenna is separated from the user, or when the electric field intensity is increased.
Also, the detecting circuit may detects the electric field intensity around the antenna, and generates the notice signal when the detected electric field intensity is lower than a reference electric field intensity.
Also, the portable phone may further include an additional antenna. In this case, the detecting circuit detects an electric field intensity around the additional antenna, and uses the detected electric field intensity around the additional antenna as the reference electric field intensity.
Also, the detecting circuit may detect the electric field intensity around the antenna and the reference electric field intensity for each of a plurality of transmission frames, and calculates a difference between the number of the electric field intensities equal to or larger than the reference electric field intensities and the number of the electric field intensities smaller than the reference electric field intensities, and generates the notice signal when the calculated difference is equal to or larger than a predetermined value.
Also, the detecting circuit includes a counter. In this case, the detecting circuit may count up the counter when the electric field intensity is equal to or larger than the reference electric field intensity, and count down the counter when the electric field intensity is smaller than the reference electric field intensity. Alternatively, the detecting circuit may count up the counter when the electric field intensity is equal to or larger than the reference electric field intensity, and count down the counter when the electric field intensity is smaller than the reference electric field intensity, and when the electric field intensity is equal to or smaller than a reference value.
Also, the detecting circuit may detect the electric field intensities around the antenna and the reference electric field intensities over a plurality of transmission frames, and calculate a first average of the detected electric field intensities and a second average of the detected reference electric field intensities, and generate the notice signal when the first average is lower than the second average.
In order to achieve another aspect of the present invention, a method of notifying degradation of communication quality in a portable phone, includes:
detecting at least one of contact of an antenna with a user of the portable phone and decrease of an electric field intensity around the antenna;
generating a notice signal based on the detecting result; and
notifying that the antenna contacts the user, to the user in response to the notice signal.
Here, it may be detected based on power of a reflected signal from the antenna that the antenna contacts the user, when a transmission signal is supplied to the antenna, and the notice signal may be generated based on the detection.
Also, a voltage of a reflected signal from the antenna may be detected when a transmission signal is supplied to the antenna, and it may be detected that the antenna contacts the user when the detected voltage is a predetermined value. In this case, the predetermined value may be preset by the user.
Also, impedance change of the antenna is detected, and it may be detected based on the detected impedance change that the antenna contacts the user.
Also, it may be detected during transmission of a transmission signal via the antenna that the antenna contacts the user. In this case, the antenna is selectively connected to the transmitting circuit, and the high frequency switch may be connected with the transmission signal.
Also, it may be notified by use of at least one of a vibrator, a speaker and an LED that the antenna contact with the user.
Also, when the antenna does not contact the user, the generation of the notice signal may be stopped.
Also, in the detecting step, the electric field intensity around the antenna is detected, and the notice signal is generated when the detected electric field intensity is lower than a reference electric field intensity.
Also, an electric field intensity around an additional antenna is detected, to use the detected electric field intensity around the additional antenna as the reference electric field intensity.
Also, in the detecting, the electric field intensity around the antenna and the reference electric field intensity may be detected for each of a plurality of transmission frames, a difference between the number of the electric field intensities equal to or larger than the reference electric field intensities and the number of the electric field intensities smaller than the reference electric field intensities may be calculated, and the notice signal may be generated when the calculated difference is equal to or larger than a predetermined value.
Also, an electric field intensity around the additional antenna may be detected to use the detected electric field intensity around the additional antenna as the reference electric field intensity.
Also, in the detecting, the counter may be counted up when the electric field intensity is equal to or larger than the reference electric field intensity, and the counter may be counted down when the electric field intensity is smaller than the reference electric field intensity.
Alternatively, in the detecting, a counter may be counted up when the electric field intensity is equal to or larger than the reference electric field intensity, and the counter may be counted down when the electric field intensity is smaller than the reference electric field intensity, and when the electric field intensity is equal to or smaller than a reference value.
Instead, in the detection, the electric field intensities around the antenna and the reference electric field intensities may be detected over a plurality of transmission frames, and a first average of the detected electric field intensities and a second average of the detected reference electric field intensities may be calculated, and the notice signal may be generated when the first average is lower than the second average.